class_docstr: Keeps track of a running mean for seen states.
  
  The filter will be used to normalize observations and will be 
  online updated according to the seen observations of all actors.
code: def as_serializable(self):
      return self.copy()
  
imports: import numpy
label_desc: Use image node_id 5 for calling the MeanStdFilter obj's underlying member method code with example usage: obj.as_serializable() and returns: self